1. Field of the Invention
The field of art to which the claimed invention pertains is processes utilizing catalytic composites. More specifically, the claimed invention relates to a process for cracking a hydrocarbon charge stock utilizing a catalytic composite comprising a zeolitic crystalline aluminosilicate dispersed in a silica-alumina matrix manufactured by spray drying a silica-alumina gel containing said zeolitic crystalline aluminosilicate and an organic polymer at a temperature sufficient to decompose the organic polymer.
2. Description of the Prior Art
The national move to remove lead from gasoline led to the investigation of high octane gasoline catalyst research. When and if refiners are required to market only unleaded gasoline, it will be necessary to upgrade the clear research octane numbers of many cat-cracked gasolines. FCC catalysts with the capability of high octane yields will help solve this problem.
For many years, heavy petroleum hydrocarbon feed stocks boiling in excess of about 400.degree. F. have been converted to lower boiling hydrocarbons in the motor fuel boiling range by heating them at temperatures in the 600.degree.-1000.degree. F. range in contact with an amorphous silica-alumina catalyst. While other composites comprising silica, e.g. silica-zirconia, silica-magnesia, etc., have been known to catalyze the cracking reaction, the silica-alumina composite has been by far the most widely accepted catalyst in the industry. More recently, improved catalysts having the capability of yielding greater proportions of high octane gasoline have been prepared by the inclusion of a finely divided zeolite, or crystalline aluminosilicate, either naturally occurring or synthetically prepared, within the amorphous silica-alumina matrix. Prior inventors have prepared, tested and compared hydrocarbon conversion catalysts comprising a finely divided crystalline aluminosilicate distributed in an amorphous silica matrix on the one hand, and in an amorphous silica-alumina matrix on the other hand. Examples of such catalysts are as described or claimed in U.S. Pat. Nos. 3,312,615; 3,392,110; 3,503,874; 3,592,778; 3,669,903; 3,696,023; 3,849,291; 3,926,778; 3,939,058; 4,001,106 and 4,100,219.
It is also known to the art to obtain a controlled pore size distribution in the amorphous matrix of a silica-alumina catalyst by incorporating an organic polymer in the gel which is the precursor of such matrix. Examples of methods for so controlling such distribution are as described or claimed in U.S. Pat. Nos. 3,322,494; 3,325,247; 3,361,526 and 3,417,028. These methods, however, enable the manufacture of alumina, silica or silica-alumina oxides having therein pore sizes lying predominantly in a range in excess of 500 Angstroms (A) in diameter. I have discovered a catalytic composite comprising a zeolitic crystalline aluminosilicate dispersed in a silica-alumina matrix, characterized by its method of manufacture, which enables the creation of pore sizes in a medium range of from about 100 to about 275 Angstroms in diameter. I have also discovered that this catalytic composite is superior to known catalysts for use in the fluid catalytic cracking process from the standpoint of product yield distribution and exceptionally high octane in the gasoline product.